productions, rising to a considerable height, with a single stem.
Trees are divided into two principal classes, namely, fruit, and timber trees; the former includes all such as are raised chiefly, or entirely, for their edible fruit; an account of which, together with their mode of cultivation, the reader will find in alphabetical order, and also in the articles Fruit-trees, Orchard, &c.—The second division comprehends those trees, the wood of which is employed in ship-building, machinery, or for other useful purposes, such as the Oak, Larch, &c.; the culture of which has been discussed under those respective heads.—See also Timber.
The growth of trees is a subject of considerable importance; but few accurate experiments have been made, in order to ascertain their annual increase in height and bulk.—In the Philosophical Transactions of the Royal Society, for 1788, Mr. Barker states, as the result of his observations, that oak, and ash-trees, grow nearly in equal proportions, increasing about 1, or 112 inch every year. He remarks, that when the annual growth amounts to one inch in height, a coat one-sixth of an inch in thickness will accrue to the tree; and as "the timber added to the body every year, is its length multiplied into the thickness of the coat, and into the girth," more timber is produced in proportion to the increasing thickness of the stem.
The health and vegetation of trees may be greatly promoted, by scraping them; by cutting away the cankered parts; and by washing their stems, annually, in the month of February or March.—Hence, Mr. Forsyth, in his ingenious "Treatise on the Culture and Management of Fruit-trees," &c. (4to. 1l. 11s. 6d.; Longman and Rees, &c. 1802), recommends fresh cow-dung to be mixed with urine and soap-suds; and the composition to be applied to the stems and branches of fruit, forest, or timber-trees, in the same manner as the ceilings of rooms are white-washed. This operation, he observes, will not only destroy the eggs of insects, that are hatched during the spring and summer, but also prevent the growth of moss; and, if it be repeated in autumn, after the fall of the leaves, it will kill the eggs of those numerous insects, which are hatched during that season and the winter; thus contributing to nourish the tree, and to preserve its bark in a fine and healthy state.—A similar practice of washing and rubbing trees was devised, many years since, by Mr. Evelyn, and Dr. Hales, who direct it to be performed first with simple water and a scrubbing brush, and afterwards with a coarse flannel: the trees, thus managed, throve uncommonly; and Mr. Marsham relates, that a beech-tree, between spring and autumn, increased 2 five-tenths inches in thickness, which was one-tenth of an inch more than an unwashed tree.—Mr. Forsyth's mixture, however, is far preferable to common water; and, if the use of the latter fluid be attended with such beneficial effects, it may be rationally concluded, that the former will be productive of still greater advantages.
In common with other objects of the vegetable creation, trees are liable to a variety of diseases; which, if not timely attended to, eventually destroy them.—Having already treated of such affections, under the heads of Canker, Moss,
